1. Field of the Invention
The invention generally relates to an optical receiver, and particularly, to an optical receiver applicable to optical fiber communication systems.
2. Related Art
Optical receivers play an important role in the field of optical fiber communication. An optical receiver receives the light transmitted through the optical fiber, transforms it into electric current corresponding to the intensity of the light. The optical receivers being currently used mainly include photo diodes. Photo diodes generally used in optical fiber communication are PIN photo diodes and avalanche photo diodes.
An optical receiver is usually designed for response only to a light of a specific frequency range. In order to prevent from detecting noise of other frequency and causing an error response, an optical receiver of prior arts uses a filter lens in front of the optical receiving portion of the photo diode. The lens is configured like receivers of general remote controls of electronic appliances. However, the filter lens has the following disadvantages when being applied in optical fiber communication:     a) Against the trend of minimizing the communication devices, the filter lens occupies much space and causes problem of space arrangement;    b) In the packaging of optical fiber communication device, the filter is hard to be fixed and makes the packaging more difficult;    c) The filter lens is sensitive to environmental conditions, easy to be damaged and shortened of its lifetime.